Chorionic villi sampling since 11th week of pregnancy Transabdominal CVS Transvaginal (transcervical) CVS – biopsy from the placenta and examining the baby's chromosomes
Chorionic villi sampling Tissue of chorionic villi Examination under the stereomicroscope
Schedule of prenatal examinations Chorionic villi sampling Amniocentesis Cordocentesis 11. 16. 20. Pregnancy (weeks) 12 th – 20 th week Ultrasound Biochemical test in 16 th week AFP, hCG, E3, PAPP 24. End of prenatal examinations
Ultrasound examination i s offer ed to all pregnant women An instrument called a transducer emits sound waves that bounce or echo off internal organs. This information is relayed to a computer, which produces an image on a nearby screen.
ultrasound scan, sonogram, or ultrasonography.
A diagnostic or screening procedure that uses high-frequency sound waves to create a picture of internal body structures, such as a developing fetus.
Nuchal translucency normal increased
on ultrasound it appears as a black space beneath the fetal skin.
this black space that you will see measured during the ultrasound scan
between 11-14 weeks of pregnancy The fetus may be affected with the Down syndrome
collection of fluid beneath the fetal skin in the region of the fetal neck and is present in all fetuses in early pregnancy.
The fluid collection is increased in many fetuses with Down syndrome and many other chromosomal abnormalities.
normally less than 2.5mm and when increased (i.e.>2.5mm) may indicate the baby has Down syndrome or another chromosomal abnormality.
If the nuchal translucency is increased then pregnant woman will be offered chorionic villus sampling or amniocentesis.
Biochemical test T riple screen or quad screen
a set of tests, which screen for genetic problems
The test determines, and also measures the levels of:
human chorionic gonadotropin (hCG)
inhibin A (for the quad screen)
This test is offered to all pregnant women.
Maternal Serum Alpha-Fetoprotein (MSAFP)
Alpha-fetoprotein (AFP) is a protein that is produced by the fetus' liver.
Between weeks 15 and 20 of a pregnancy, a maternal serum alpha-fetoprotein (MSAFP) screen will be offered.
The quantity of AFP that is considered normal depends upon many variables, including age, weight, race, and stage of pregnancy. Insulin-dependent diabetes also influences AFP levels. Of those women whose tests show high or low levels of AFP, only two or three in 100 will have a child with a birth defect .
Up to 10% of results are positive, meaning you have high- or low-AFP levels. With a positive AFP, additional tests will be suggested to help determine the cause.
Amniocentesis 15 th – 16 th week of pregnancy
can diagnose or rule out many possible birth defects.
Most often, it's used to spot common genetic defects (such as Down syndrome) and neural tube defects.
is usually performed at 15 to 18 weeks gestation, although it can be done as early as 11 or 12 weeks.
Amniocentesis is typically offered to women who
Will be 35 or older when they give birth.
Have a screening test or exam result that indicates a possible birth defect or other problem.
Have had birth defects in previous pregnancies.
Have a family history of genetic disorders.
Risk of amniocentesis
About one woman in every 200-400 women miscarry as a result of amniocentesis.
Amniocentesis done during the first trimester carries a greater risk for miscarriage than amniocentesis done after the 15th week.
Less than one woman in every 1,000 women develop a uterine infection after amniocentesis.
percutaneous umbilical blood sampling (PUBS)
umbilical vein sampling
fetal blood sampling
since 20th week of pregnancy
diagnostic procedure in which a doctor extracts a sample of fetal blood from the vein in the umbilical cord.
Th e fetal blood can be analyzed to detect chromosomal defects or other abnormalities.
Cordocentesis – advantages and risks
results are usually ready much faster than with amniocentesis. With cordocentesis, the results may be ready within 48 hours. With amniocentesis, results can take about two weeks.
The miscarriage rate after cordocentesis is about 1 – 2%.
As with amniocentesis, there is a risk of infection, cramping, and bleeding.
Prenatal examinations fetus chorion amnion umbilical cord Chorionic villi sampling (CVS) Amniocentesis Cordocentesis 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. End of all prenatal examinations Weeks of pregnancy
For all of invasive prenatal samplings written consent of the mother is necessary.
Examinations of the fetus
Examination of an individual after the birth
Indications for postnatal chromosomal analysis
Possible chromosomal abnormality
Multiple anomalies or growth retardation
Unexplained mental retardation
Infertility or multiple miscarriages
Death of a fetus, death of a newborn child
Occurrence of tumors
Tissues for postnatal karyotyping
Bone marrow (leukemia)
Autopsy material (in case of a death of patient)
How to take a blood sample for chromosomal analysis?
Disinfect the site of injection with alcohol (not iodine solution)
The blood should be taken to heparin tube (heparin prevents blood clotting)
Cultivation of peripheral blood lymphocytes
Add phytohemaglutinin to medium – highly immunogenic compound - stimulates blood lymphocytes proliferation
At the end of cultivation – application of colcemide (disrupts the mitotic spindle)
Solid staining of chromosomes We use only Giemsa-Romanowski solution 6 – 12 13 – 15 19 – 20 21 – 22 4 – 5
G-banding (GTG) Trypsin + Giemsa
Each G-band has concrete number : Xq27.3 Chromosome X with G-bands
Another methods of chromosome staining
R-banding (reverse bands – opposite to G-bands)
Q-banding (quinacrin banding)
C-banding (staining of constitutive heterochromatin
Ag-NOR (staining of satellites in acrocentric chromosomes)
High resolution technique
Special cultivation method that allows isolation of prometaphase chromsomes
Very long chromosomes
Identification of small rearrangements is possible
Arrange a karyotype (small box with chromosome photos + table with chromosomes)
Observe human G-banded chromosomes (box with slides)
Find the chromosomes or interphase nuclei on the slide using 10x objective lens.
Change the objective magnification into 40x and observe chromosomes.
Compare the picture in the microscope with adjacent photo.
Results will be controlled by Mrs. Tůmová, Dr. Diblík or Dr. Kočárek.
Description of a normal karyotype according to cytogenetic nomenclature (ISCN 200 5)
Male … 46,XY
Female … 46,XX
Total number of all chromosomes, sex chromosomes 46,XY